From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753483AbeBKP2x (ORCPT ); Sun, 11 Feb 2018 10:28:53 -0500 Received: from aserp2120.oracle.com ([141.146.126.78]:58146 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751077AbeBKP2w (ORCPT ); Sun, 11 Feb 2018 10:28:52 -0500 Subject: Re: [PATCH 2/2] xen: xenbus: WARN_ON XS_TRANSACTION_{START,END} misuse To: Simon Gaiser , xen-devel@lists.xenproject.org Cc: Juergen Gross , linux-kernel@vger.kernel.org References: <20180207222236.7434-1-simon@invisiblethingslab.com> <20180207222236.7434-2-simon@invisiblethingslab.com> <8a0fd059-7acf-3279-10f9-649c19522e2a@oracle.com> <66103cca-321e-6950-2083-6f5d068e12e6@invisiblethingslab.com> From: Boris Ostrovsky Message-ID: <0bf1782a-b7c4-1775-c2cb-6e68fe62a199@oracle.com> Date: Sun, 11 Feb 2018 10:28:38 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <66103cca-321e-6950-2083-6f5d068e12e6@invisiblethingslab.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8802 signatures=668668 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=879 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1711220000 definitions=main-1802110205 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/10/2018 08:27 PM, Simon Gaiser wrote: > Boris Ostrovsky: >> On 02/07/2018 05:22 PM, Simon Gaiser wrote: >>> + users_old = xs_state_users; >>> xs_state_users--; >>> if ((req->type == XS_TRANSACTION_START && req->msg.type == XS_ERROR) || >>> req->type == XS_TRANSACTION_END) >>> xs_state_users--; >>> + if (WARN_ON(xs_state_users > users_old)) >> >> >> WARN_ON_ONCE()? > > Since we "fix" the wrong decrement by clamping at zero it should not > happen immediately again. But if you prefer _ONCE I can change it. > If this error can happen once then someone at least theoretically can construct a case when it is repeated. So let's switch to _ONCE() variant. Thanks. -boris